Update configurable products in Magento via CSV -

Update configurable products in Magento via CSV -

i'm making magento webshop uses dataflow import of csv create products automatically our seperate stock management system.

when products imported first time, there no errors , import process working perfectly. - when import them again, update stock, description etc., configurable products gives me error:

sqlstate[23000]: integrity constraint violation: 1062 duplicate entry '875-135' key 'unq_catalog_product_super_attribute_product_id_attribute_id'

is there way create overwrite correctly?

magento csv import configurable